1. Field of the Invention
The present invention relates to explosive compositions of the water-in-fuel emulsion type in which an aqueous oxidizer salt solution is dispersed as a discontinuous phase within a continuous phase of a liquid or liquefiable carbonaceous fuel.
2. Description of the Prior Art
Water-in-fuel emulsion explosives are now well known in the explosives art and have been demonstrated to be safe, economic and simple to manufacture and to yield excellent blasting results. Bluhm, in U.S. Pat. No. 3,447,978, disclosed an emulsion explosive composition comprising an aqueous discontinuous phase containing dissolved oxygen-supplying salts, a carbonaceous fuel continuous phase, an occluded gas and an emulsifier. Since Bluhm, further disclosures have described improvements and variations in water-in-fuel explosive compositions.
These include U.S. Pat. Nos. 3,674,578, Cattermole et al; 3,770,522, Tomic; 3,715,247, Wade; 3,765,964, Wade; 4,110,134, Wade; 4,149,916, Wade; 4,149,917, Wade; 4,141,767, Sudweeks and Jessup; Canadian Patent. No. 1,096,173, Binet and Seto; U.S. Pat. Nos. 4,111,727, Clay; 4,104,092, Mullay; 4,231,821, Sudweeks and Lawrence; 4,218,272, Brockington; 4,138,281, Olney and Wade; and 4,216,040, Sudweeks and Jessup. Mullay, in 4,104,092, describes a jelled explosive composition which is sensitized by means of an emulsion. This composition may contain, as an additional sensitizer, nitromethane, for example. Sudweeks et al, in U.S. Pat. No. 4,141,767, suggest that aliphatic nitro compounds can be used as the fuel phase of an emulsion blasting agent but no example demonstrating utility is provided, nor is any claim made to such a material. Sudweeks et al, again in U.S. Pat. Nos. 4,231,821 and 4,216,040 make reference to aliphatic nitro compounds as fuels for emulsion explosives, but again no examples are provided. Cattermole et al, in U.S. Pat. No. Re. 28,060, suggest that nitroalkanes, such as nitropropane, may be used as the organic fuel continuous phase in an emulsion type blasting agent without any exemplification thereof. Tomic, in U.S. Pat. No. 3,770,522, makes the same unsupported suggestion.
While it has been generally recognized in the art that nitroalkane compounds would be excellent candidates as the fuel phase for emulsion explosives because of their low oxygen value, high energy nature and low price, no useful and stable emulsion explosive containing these fuels has yet been produced for practical application. The principal difficulty in compounding such an explosive has been the failure to discover suitable surfactants to emulsify the nitroalkane in stable emulsion explosives. Heretofore, when used, nitroalkanes have been employed only in small amounts and in combination with conventional oil/wax fuels.